Well, I haven't given up, but I still haven't found the cause of the rough idle.
Last night I did the following:
1) swapped the coil packs - no change.
2) Swapped the MAF sensor - no change.
3) Plugged the vacuum hoses connected to the fuel vapor canister (because I can hear the solenoid rattling sometimes) - no change.
4) Checked the wires and plugs again - all wires look ok and measure between 4k Ohms and 7.5 KOhms. All plugs were grayish white and the electrode wear looked normal but I regapped them to .060" again anyway - no change.

Since none of the plugs look to be oild fouled, or otherwise damaged, it doesn't seem logical that one injector could cause a lean condition for all cylinders.

So it still seems as if there'* a vacuum leak somewhere or maybe it'* a fuel pump/fuel pressure regulator porblem...

Filter?

Test the fuel pressure like normal and if you get good results a deadhead test might be helpful.

The fuel filter was already replaced.

What'* a "deadhead" test?

That'* where you cover the return line to see what the pump can make. I went ahead and pulled my finger off the return line at 65ish psi. My pump can make 85+psi out of the car. See what yours can do.

I finally found the cause of the rough idle and fixed it.
After checking and replacing other parts with no improvement, I replaced the supercharger base gasket and tightened the vacuum block on top of the supercharger and now the engine runs like it did when I bought it.

Hey, It could be a vacuum leak....